This effectively disables "--help", replacing it with just a stand-in
string.
The upshot is that it makes the test suite immune to whether or not it
can find the documentation - until now it needed to *not* find it,
which is weird.
(also it saves some useless lines)
Fixes#11270
We require 3.19
This also makes skipped tests visible, which showed that the
print-help test was never run because the REQUIRES line was off.
In sh-mode, bash's `command -v` returns true if *all* commands exist.
See the changelog additions for user-visible changes.
Since we enable/disable terminal protocols whenever we pass terminal ownership,
tests can no longer run in parallel on the same terminal.
For the same reason, readline shortcuts in the gdb REPL will not work anymore.
As a remedy, use gdbserver, or lobby for CSI u support in libreadline.
Add sleep to some tests, otherwise they fall (both in CI and locally).
There are two weird failures on FreeBSD remaining, disable them for now
https://github.com/fish-shell/fish-shell/pull/10359/checks?check_run_id=23330096362
Design and implementation borrows heavily from Kakoune.
In future, we should try to implement more of the kitty progressive
enhancements.
Closes#10359
